Cited By (since 1996):10, Ecology,
Seaweeds, CODEN: JEMBA, The effect of the common bat star, Asterina miniata (Brandt) on recruitment of the giant kelp, Macrocystis pyrifera C. Agardh, was addressed through laboratory grazing experiments, a field experiment, and modeling of feeding behavior. In the laboratory, Asterina miniata significantly decreased the density of sporophytes that developed from 1-wk-old gametophytes as well as the percent cover of 2-, 6-, and 7-wk-old sporophytes. All grazed blades remaining at the end of these experiments subsequently died. Small scale variability in spore settlement and sporophyte development were also evident in the laboratory. Bat star density significantly affected short-term kelp recruitment during a large-scale field experiment. Simple modeling suggested that high densities of Asterina miniata could graze nearly 100% of the bottom over the 90-day experiment. However, visible recruitment was seen in less than 30 days, and over this time, 36% of the substratum was predicted to have remained ungrazed. Macrocystis pyrifera of 1 to 3 cm in length may thus obtain a refuge in size from bat star grazing through rapid growth. These results indicate this generalist grazer can affect giant kelp recruitment but that even under high grazing pressure numerous plants survive. Bat star grazing probably does not contribute to large-scale differences in adult plant density but may contribute to small-scale patterns of dispersion., ,

In situ chemical mapping of dissolved iron and manganese in hydrothermal plumes,

Description

Hydrothermal vents along mid-ocean ridges are an important source of elements such as lithium, silicon, manganese and iron to the world's oceans. The venting produces both episodic and steady-state hydrothermal plumes with unique thermochemical signatures in the mid-water column. The particulate phases in these plumes (predominantly iron oxides and hydroxides) also scavenge phosphorus, vanadium, arsenic, lead, polonium and several rare-earth elements from sea water. Thus, on a global scale, hydrothermal plumes are both a source for some elements and a sink for others. Ultimately, the particulate metals precipitated from plumes form extensive regions of metalliferous sediments over the crests and flanks of mid-ocean ridges. Although the metalliferous sediment coverage is vast and well documented, only a tiny fraction of the vents responsible for these sediments have been located (Fig. 1a). To date, both the number and location of hydrothermal vents and the detailed distribution of chemical constituents within the resultant plumes are poorly understood because of under-sampling of the mid-ocean ridges and the overlying waters. Here we present the results of high-resolution mapping of the chemical and thermal characteristics of hydrothermal plumes in near real time using a novel submersible chemical analyser (Scanner) and a conductivity/temperature/depth/transmissometer instrument package (CTDT). We show that the kinetics of iron oxidation in the plume can be used to constrain estimates of the plume's age, and that variation in the ratio of manganese content to excess heat can be explained by the mixing of several different vent fluids., Cited By (since 1996):31, CODEN: NATUA, ,

Cobalt and copper distributions in the waters of Santa Monica Basin, California,

Description

The trace metals cobalt and copper are removed from the oceans interior by scavenging on to particle surfaces, but the mechanisms for removal of these two metals are probably quite different. Cobalt appears to be scavenged by manganese oxide particles, whereas organic compounds are the main carrier phase for copper. Remobilization of these metals in marine sediments therefore proceeds by different pathways. The differences in the pathways of remobilization are accentuated in oxygen-deficient environments: manganese oxide reduction is accelerated at low oxygen levels and organic carbon is preserved. Cobalt fluxes from sediments underlying oxygen-deficient waters should be enhanced and copper fluxes reduced. We report here measurements of the cobalt and copper distributions in the waters of an oxygen-deficient marine basin in the Southern California Bight. Cobalt concentrations near the bottom are raised four times above the background level, whereas copper concentrations show no increase. These measurements confirm features of existing models for the oceanic cycles of these metals., Cited By (since 1996):18,
Oceanography, CODEN: NATUA, ,

Modeling the upper ocean dynamics in the Subantarctic and Polar Frontal Zones in the Australian sector of the Southern Ocean,

Description

A one-dimensional (1-D) mixed layer model (the Chen scheme) was applied in the Subantarctic Zone (SAZ) and the Polar Frontal Zone (PFZ) to simulate the upper ocean dynamics. The model was forced with 4 years data of the heat fluxes, freshwater fluxes, and wind stresses from the National Centers for Environmental Prediction. In both the SAZ and PFZ, the 1-D model was capable of reproducing the amplitude of the seasonal sea surface temperature (SST) and the seasonality of the mixed layer depth (MLD). The shallowest MLD was found in January-February (20 m in the SAZ, 35 m in the PFZ), and the deepest MLD was found between August and October (600 m in the SAZ, 160 m in the PFZ). The summer MLD was shallower in the SAZ than in the PFZ due to the lower wind stress. However, the shallower winter MLD in the PFZ than in the SAZ was due to the strong stratification in the water below the mixed layer. In the SAZ, variability in the wind stress was the dominant term driving the fluctuation in MLD in the summer, but variability in the heat flux was the major factor controlling the timing of the deepening and shoaling of the mixed layer in the winter. In the PFZ both the variability in the wind stress and the heat flux dominated the variability of the MLD in both the summer and the winter. Copyright 2001 by the American Geophysical Union., Cited By (since 1996):8, , , Downloaded from: http://onlinelibrary.wiley.com/doi/10.1029/2000JC000357/pdf (9 June 2014).

Sediment-water exchange of total mercury and monomethyl mercury in the San Francisco Bay-Delta,

Description

Five field trips were conducted in the San Francisco Bay-Delta between May 2000 and October 2001 to investigate the sediment-water exchange of total mercury (Hg) and monomethyl mercury (MMHg). Solid-phase Hg averaged ∼1 nmol g -1 and did not show any variability with depth or time or among sites. In contrast, solid-phase MMHg showed considerable vertical, temporal, and spatial variability (0.4-66 pmol g -1), with the highest values occurring at a peat-rich environment in May 2001, suggesting that MMHg production was largely controlled by temporal factors and habitat type. In pore water, both Hg and MMHg concentrations were generally elevated near the sediment-water interface during warm months. Sediment-water exchange flux of MMHg, determined with benthic chamber deployments, ranged from -92 to 850 pmol m -2 d -1, with higher values occurring in May. In most cases, diffusional fluxes of Hg and MMHg, estimated with the use of interfacial concentration gradients, constituted only a minor portion of the measured fluxes, suggesting the importance of advective processes on sediment-water exchange. Surface-water transect and time series studies conducted in Franks Tract support the commonly held belief that wetland and marsh regions are major sources for MMHg within the Delta. The integrated sediment-water fluxes of Hg and MMHg in the study area were estimated to be 130 and 6 mmol d -1, respectively, and the benthic input was as important a source of Hg and MMHg as the riverine input within the Delta during low-flow months., Cited By (since 1996):63, Rocks and Cores,
Oceanography, CODEN: LIOCA, ,

A shark antibody heavy chain encoded by a nonsomatically rearranged VDJ is preferentially expressed in early development and is convergent with mammalian IgG

Description

In most vertebrate embryos and neonates studied to date unique antigen receptors (antibodies and T cell receptors) are expressed that possess a limited immune repertoire. We have isolated a subclass of IgM, IgM1gj, from the nurse shark Ginglymostoma cirratum that is preferentially expressed in neonates. The variable (V) region gene encoding the heavy (H) chain underwent V-D-J rearrangement in germ cells "germline-joined"). Such H chain V genes were discovered over 10 years ago in sharks but until now were not shown to be expressed at appreciable levels; we find expression of H1gj in primary and secondary lymphoid tissues early in life, but in adults only in primary lymphoid tissue, which is identified in this work as the epigonal organ. H1gj chain associates covalently with light (L) chains and is most similar in sequence to IgM H chains, but like mammalian IgG has three rather than the four IgM constant domains; deletion of the ancestral IgM C2 domain thus defines both IgG and IgM1gj. Because sharks are the members of the oldest vertebrate class known to possess antibodies, unique or specialized antibodies expressed early in ontogeny in sharks and other vertebrates were likely present at the inception of the adaptive immune system., Cited By (since 1996):41, CODEN: PNASA, Fish and Fisheries

A slumping event that occurred on permanent transect lines from 12- to 30- m depth located at Arrival Heights, McMurdo Sound, Antarctica in 1993, provided an opportunity to examine the effects of sediment-mediated disturbance on the benthic invertebrate fauna. The disturbance had a particularly significant impact on the soft coral Alcyonium paessleri, which resulted in 84% colony mortality downslope from the slump site compared to an average annual mortality rate of 14% on control transects. In contrast, anchor ice at the same site accounted for removal of 5% of the population in 1992. Laboratory experiments with A. paessleri colonies under conditions of periodic sediment resuspension indicate that the soft corals are susceptible to this form of disturbance. Our observations suggest they are capable of shedding fine silt in the laboratory, which might ex-plain the presence of A. paessleri in soft-sediment sites around McMurdo Sound. However, scarring by larger gravel in laboratory assays was slow to heal and may account for much of the colony mortality we observed. Several invertebrate-barren rocky benthic regions in McMurdo Sound were suggestive of historical slumping events. Given the removal of the smaller grain size sediments from these areas - a typically slow process it appears these communities are slow to recover. The long-term effects of sedimentation on the benthic communities are unknown, but the impact on A. paessleri, one of the most common and fastest growing species, suggests this disturbance mechanism could lead to significant restructuring of these communities., Cited By (since 1996):13, Invertebrates, CODEN: POBID, ,